This invention relates generally to yokes in flexible shaft assemblies with clamp bolts for securing the yokes on shafts. More particularly, it relates to slap yokes, such as are used in vehicle steering columns and other rotary-drive devices, having clamp bolts which not only clamp the yoke to the shaft but also help to position the shaft within the yoke during clamping.
Rotary shafts are commonly connected using yokes with universal joints to allow for variable misalignments between coupled members. Slap yokes are often used for such connections. They are formed in a U-shaped configuration to provide a socket having holes in its walls for a transverse bolt to provide clamping force to hold the yoke on the shaft. During assembly, the shaft is laid into the U-shaped socket, pressed against the closed side of the socket, and clamped in place by tightening a bolt inserted through the holes in the walls of the socket. The shaft is also usually formed with an undercut section to coincide with the bolt location and to confine the axial location of the yoke on the shaft within a designed range. It is necessary to force the shaft against the bottom of the U-shaped socket in order to correctly align the yoke and the shaft so that the axes of the two parts are concentric. This is usually accomplished by features of the yoke or bolt which provide a radial force against the shaft, from the open side of the U-shaped portion of the yoke, to force the shaft against the closed side.
One approach to radially pressing the shaft against the socket is to provide wedge-shaped features at the sides of the yoke which bear against the shaft when the bolt is tightened and force the bolt down against the yoke. Another method employs a nut and a cam bolt which has a single or multi-lobed axial form along its center and which wedges by cam action against the shaft when torque is applied to the bolt. These and other even more complex methods have been successfully used to provide the required alignment and clamping. All, however, require handling of an excessive number of pieces during installation in close quarters, or they require components which include costly features.
In general, slap yokes for steering columns are provided with a fixed nut, a rotatable trapped nut, or a threaded hole in the second wall. This is done so that the assembly can be completed and tightened from one side; because of the difficulty of reaching into the very limited space available in the vehicle. Because of the cramped assembly conditions, it is necessary to have some way of assuring, without being able to actually see it, that the shaft is firmly seated in the socket of the yoke before the clamp bolt is tightened.
The foregoing illustrates limitations known to exist in present rotary-drive shaft connectors. Therefore, it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a shaft depressor for use in a slap yoke with a U-shaped socket for receiving a shaft, a clamp bolt extending between a first side and a second side thereof, said shaft depressor comprising a cylindrical bushing having an inside diameter sized to fit over said clamp bolt, and means for pressing said shaft into the closed portion of said socket.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.